Engines historically have had solid rubber mounts to isolate engine vibration from the vehicle cabin and chassis, where the rubber naturally absorbed vibrations from the engine. However, in performance and high end cars, if rubber is too compliant, then certain vehicle maneuvers may cause high loads, and this may stress joints in the vehicle, for example in the exhaust system. Hence, tunable active engine mounts have been developed that may be controlled to change dampening characteristics depending on engine load.
As an example, the active engine mounts may be configured to be soft (e.g. dampening mode) at engine idle to absorb undesired vibrations. However, at higher engine speeds, the active engine mounts may be configured to stiffen (e.g. stiffening mode), to limit undesired engine motion, which may prevent stress on exhaust joints, for example. Accordingly, active engine mounts may achieve low noise, vibration, and harshness (NVH) at idle, and may further reduce NVH and prevent undesired stress at high loads. Overtime, the active engine mounts may degrade due to active engine mount aging, for example. As a result, the undesired engine vibrations may not be absorbed as effectively. Further, if the undesired vibration is not appropriately absorbed/dampen, engine performance may be reduced, leading to reduced fuel economy and overall decrease in engine efficiency.
The inventors herein have recognized these issues, and have developed systems and methods to at least partially address the above issues. In one example, the conditions of active engine mounts may be monitored and diagnosed by a method for a vehicle comprising: spinning an engine, which drives the vehicle, unfueled using torque from an electric motor while selectively deactivating engine valves and/or shutting-off fueling to an engine cylinder while adjusting an active engine mount responsive to a request to monitor the active engine mount; and indicating degradation of the active engine mount based on an amount of vehicle chassis vibration during the spinning. In this way, active engine mounts degradation may be reliably identified and addressed in a timely manner.
As an example, an autonomous or hybrid vehicle system may include an engine and a transmission coupled to vehicle chassis via active engine mounts. The active engine mounts may be vacuum-regulated engine mounts that counter engine vibration by operating in a first, dampening mode during engine idle condition and operating in a second, stiffening mode at higher engine speed/load condition to reduce intensity of engine vibration. In particular, during vehicle static condition, the vehicle/engine vibration may be induced via a non-combustion mode or a degraded combustion mode. Inducing vehicle vibration via non-combustion mode may include spinning an engine unfueled while selectively deactivating valves of engine cylinders (i.e. selectively activating variable displacement engine (VDE) mode in a periodic fashion). Alternatively, vehicle vibration may be induced via shutting off fueling to one or more preselected engine cylinders to stimulate a degraded combustion events (i.e. misfire). A controller may then adjust the active engine mounts to operate in a first, dampening mode or a second, stiffening mode for a duration during the inducing, and at the same time, engine vibration patterns may be monitored via one or more vibrational sensors over the duration. If the monitored vibration patterns are within a threshold when operating in the first mode and above a threshold when operating in the second mode, then the active engine mounts are indicated to be functioning as desired. However, if the monitored vibration are within a threshold for both operating modes, then it may be inferred that the active engine mounts are stuck in the dampening mode. Alternatively, if the monitored vibrations are above a threshold for both operating modes, then it may be inferred that the active engine mounts are stuck in the stiffening mode.
In this way, active engine mounts may be accurately and reliably diagnosed, enabling engine mounts degradation to be better predicted. The technical effect of adjusting active engine mounts to a selected operating mode while inducing vehicle vibration and monitoring the vibrational pattern following the adjusting is that the actual operating state of the active engine mounts may be better identified. By timely diagnosing active engine mounts, active engine mount health may be improved, reducing undesired NVH-related issues and enabling improved engine performance.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.